The present invention is generally related to a video camera apparatus with using an image sensor, e.g., a CCD. More specifically, the present invention is directed to a video camera apparatus capable of simply extracting brightness information used in an auto-iris control.
In general, video camera apparatuses with employing CCDs (charge-coupled devices) as solid-state image pick-up devices are widely marketed. These video camera apparatuses are equipped with various functions, for instance, auto-iris control (automatic diaphragm control), auto-focus control, auto-white balance control, and the like. These functions are automatically controlled by employing the feedback loops.
A typical automatic function controlling arrangement of the conventional video camera apparatus is represented in FIG. 1 and FIG. 2.
In the first circuit arrangement of FIG. 1, in response to imaging light entered via a lens system 21 into a CCD 22, for example, the respective pixel signals R (red), G (green), and B (blue) are outputted from this CCD 22.
The gains of these R, G, B pixel signals are controlled by an AGC (auto-gain control) circuit 23, and thereafter the gain-controlled R, G, B pixel signals are converted into digital pixel data by an A/D converter 24. Then, after the digital clamping process is performed to these digital pixel data by a clamp circuit 25, preselected gains are applied to the respective R, G, B pixel data by a white balance amplifier 26 in order to perform the white balance.
After the gain control for the white balance control is carried out, each of the resulting pixel data is supplied to a luminance signal (Y-signal) processing circuit 27 and a chrominance signal processing circuit 28.
In this luminance signal processing circuit 27, the camera process operations such as the xcex3 (gamma)-correction and the white clipping are carried out with respect to the R, G, B pixel data supplied to this luminance signal processing circuit 27, and further a luminance signal (Y-signal) is produced by executing the matrix calculation process with using the R, G, B pixel data. Thus, this luminance signal functioning as the imaging data is supplied from this luminance signal processing circuit 27 to the post-stage circuits.
Also, the chrominance signal processing circuit 28 produces color difference signals xe2x80x9cRxe2x88x92Yxe2x80x9d and xe2x80x9cBxe2x88x92Yxe2x80x9d by performing the matrix calculation process with employment of the camera-processed R, G, B pixel data, and thereafter outputs these color difference signals xe2x80x9cRxe2x88x92Yxe2x80x9d and xe2x80x9cBxe2x88x92Yxe2x80x9d to the post-staged circuits.
The gains which are applied to the respective color pixel data by the white balance amplifier 26 are controlled by the feedback loop. To execute this feedback control, it is required to detect the levels as these color signals, i.e., R (red) signal, G (green) signal, and B (blue) signal. To this end, the R signal, the G signal, and the B signal are extracted from the chrominance signal processing circuit 28, and signal levels thereof are detected by an auto-white balance detecting unit 31. The level information DAWB of the respective color pixel data are supplied to a controller 32 constituted by a microcomputer (not shown in detail), and the gains of the respective colors used in the white balance are calculated. For example, the gains with respect to the R signal and the B signal are calculated in order that both the R signal and the B signal own the same signal levels with regard to the level of the G signal under such a condition that the reference imaging object is imaged by the video camera apparatus. Then, the white-balance gain control information SAWB is supplied to the white balance amplifier 26 so as to control, for example, the gain of the R signal and the gain of the B signal.
On the other hand, the luminance information of the image signals are used in the auto-iris operation and the auto-focus operation. That is, the luminance signal produced in the luminance signal processing circuit 27 is extracted to be supplied to the auto-iris detecting unit 29 and the auto-focus detecting unit 30.
In the auto-iris detecting unit 29 and the auto-focus detecting unit 30, the diaphragm controlling information DAEand the focus controlling information DAF are extracted, and then are supplied to the controller 32.
In response to the diaphragm (iris) controlling information DAE, namely the brightness information, the controller 32 supplies an iris control signal SAE to a timing generator 34 and an AGC circuit 23 in order to control the CCD exposure time and the gains, so that the iris control can be performed.
Also, in response to the focus controlling information DAF, namely, such information corresponding to the focusing condition of the lens system 21, the controller 32 supplies a focus control signal SAF to a focus motor 33 so as to move a focus lens employed in the lens system 21, so that proper focusing conditions can be realized.
FIG. 2 schematically shows another structural example of the conventional camera apparatus. It should be noted that the same reference numerals shown in FIG. 1 will be employed as those for denoting the same, or similar circuit portions, and therefore, descriptions thereof are omitted.
In this conventional video camera apparatus, a luminance signal producing unit 35 is provided independent from the luminance signal processing circuit 27 in order to acquire brightness information and the like in the auto-iris detecting unit 29 and the auto-focus detecting unit 30. In other words, the respective R, G, B pixel data outputted from the white balance amplifier 26 are supplied to the luminance signal producing unit 35 to thereby produce such a luminance signal used in the auto-iris detecting operation and also the auto-focus detecting operation.
The above-described conventional circuit arrangements own the below-mentioned problems.
In the case of the circuit arrangement shown in FIG. 1, the luminance signal used in the auto-iris detecting operation and in the auto-focus detecting operation is derived from the luminance signal processing circuit 27. This luminance signal corresponds to such a signal produced by executing a large number of process operations to the original pixel signal in the luminance signal processing circuit 27. As to the auto-iris operation, this auto-iris operation is preferably controlled based on the signal which is substantially equal to the original pixel signals directly outputted from the CCD 22. However, in this conventional video camera apparatus, the luminance signal produced by executing these various process operations to the original pixel signals within the luminance signal processing circuit 27 must be employed.
On the other hand, in another conventional video camera apparatus with separately employing the luminance signal producing unit 35 as shown in FIG. 2, since this luminance signal producing unit 35 merely produces such a luminance signal exclusively directed to the auto-iris/auto-focus detecting purposes, the unnecessary process operations for these detecting operations can be omitted. However, in principle, this conventional video camera apparatus necessarily requires the circuit for performing the luminance signal producing calculations similar to the calculations executed in the luminance signal producing circuit 27. In other words, since two sets of the similar circuit arrangements are required in this video camera apparatus, there is a useless circuit arrangement.
Also, in any cases of FIG. 1 and FIG. 2, the auto-white balance control loop is mixed with the auto-iris control loop.
In particular, it is desirable to execute the white balance control at the pre-stage circuit, rather than at the luminance/chrominance signal process operations. Accordingly, there is no way except that the luminance signal used in the iris control operation is derived at the post-stage circuit of the white balance amplifier 26.
On the other hand, in principle, the iris control implies that brightness is controlled, whereas the white balance control implies that color balance is controlled. When brightness is changed, a color change will occur in response to this brightness change.
As a consequence, as previously described, since the luminance signal used in the iris control should be derived from the post-stage circuit of the white balance amplifier 26 in the conventional video camera apparatuses, the operations of the respective control loops may give adverse influences to the operations of other control loops. Therefore, there is such a drawback that the respective control loops can be hardly converged.
The present invention has been made to solve these problems, and therefore has an object to provide a video camera apparatus capable of simply extracting, in particular, brightness information used to perform an auto-iris control operation, and further capable of effectively executing control loop operations in order that a plurality of such control loops giving adverse influences to each other are not mixed with each other.
To achieve the above-described object, a video camera apparatus, according to an aspect of the present invention, is comprised of pseudo-luminance information producing unit for multiplying the respective pixel information which is outputted from the solid-state imaging element and is acquired before being inputted into a image signal processing unit to thereby produce a pseudo-luminance information signal; and iris control unit for performing an iris control based on the pseudo-luminance information signal.
In the case that a color filter of the solid-state imaging element is made of a G checkered pattern and R/B line sequential type color filter in which G (green) filters are arranged in a checkered pattern, and R (red) filters and B (blue) filters are alternately arranged every line, the pseudo-luminance information producing unit produces the pseudo-luminance information signal by executing the following calculation: 2G+R+B.
Also the pseudo-luminance information producing unit produces luminance information by multiplexing the respective pixel information which is acquired before being inputted into a white balance control unit including a white balance amplifier.
Since the pseudo-luminance information corresponding to the multiplication value of the pixel information contains the brightness information as the pseudo-luminance signal, the iris control operation can be carried out by employing the multiplication value of the pixel information. Also, in this case, since the luminance signal is not employed in this video camera apparatus, the pixel information acquired before being inputted to the white balance amplifier can be employed.